Coronary artery stenosis is primarily due to deposits of cholesterol, calcium and fibrotic tissue, with the fibrotic tissue typically being the dominant of the three components. It happens that a large proportion of stenoses are formed as eccentric lesions (i.e. lesions that do not extend completely around the circumference of the affected body vessel). A suitable remedy would effectively treat an eccentric stenosis without adversely affecting healthy, non-diseased tissue.
Dilation of stenoses using standard angioplasty balloons has enjoyed widespread acceptance in the treatment of stenoses, however, this treatment protocol suffers from a high rate of restenosis. Recent studies, however, indicate that the rate of restenosis can be reduced if the stenosis that is being dilated is also incised. With incision, some stenoses can be more easily flattened, and the likelihood of damaging the artery during dilation may be reduced.
For the reasons cited above, cutting balloons may be used as a replacement for conventional percutaneous transluminal coronary angioplasty (PTCA) procedures in the revascularization of coronary and peripheral vessels. In particular, the cutting balloon mechanism is unique in that the balloon pressure is distributed over one or more incising elements (e.g. atherotomes). Functionally, the incising elements act as stress concentrators and cut initiators in PTCA atherectomy procedures. In some cases, PTCA atherectomy procedures may be effective in reducing vessel recoil and vessel injury and in lowering the rate of restenosis, as compared to conventional PTCA procedures.
U.S. Pat. No. 5,196,024 which issued to Barath on Mar. 23, 1993 for an invention entitled “Balloon Catheter With Cutting Edge,” discloses an inflatable angioplasty balloon having a number of elongated atherotomes (e.g. 8 blades) mounted longitudinally on the surface of the balloon and distributed uniformly around the circumference of the balloon. During an inflation of the Barath balloon, the atherotomes move radially to induce a series of longitudinal cuts into the surface of the artery that are somewhat uniformly distributed around the circumference of the artery. When incising an eccentric lesion, however, it is typically desirable to incise only the diseased portion of the vessel. For these cases, a device designed to incise uniformly around the circumference of the vessel may be unsuitable.
In light of the above, the present invention is directed to unique devices and methods for incising a biological material in a body conduit. In addition, the present invention is directed to directional cutting balloons and corresponding methods of use which are relatively simple to implement and comparatively cost effective.